Chapter 1: introduction
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- Figures 6.2:Observed real time flow data for 2011
- Figure 6.5: Tamor River flow data below the Kabeli-A a tailrace with and without operation.
- Mitigation
- Recreation/Religious and Cremation requirements
- Figure 6.6: Location of Religious and Cremation Sites downstream the Dam
- Tamor stretch between confluence and down to powerhouse
- Calculations of Environmental flow
- Table 6.5: In-stream flow for fish, wildlife, and recreation (Tennant 1975)
- Oct.-Mar. Apr.-Sept.
- Computation of Tenant, 1975 to Kabeli River for fair and degrading EF
6.1.1.2 Operation PhaseI. Disturbance to fish and aquatic species and its habitat due to the obstruction created by the proposed weir The diversion structure and creation of reservoir in the operation phase divide the exiting river morphology into following sections:
As the existing aquatic life co-exists with the undisturbed river morphology and natural flow regime, once in operation, there will be some level of disturbance in their lifecycle due to morphological changes and water conditions on the modified river stretches. Changes in aquatic life are likely to occur in the reservoir section, the dewatered section and the discharge fluctuation zone, especially from November to May every year. In these months, the water in the dewatered section will come mainly from the environmental flow release from the diversion weir, and the water level and discharge fluctuation below the tailrace will fluctuate on a daily basis. In the reservoir section, the water will show twice a day water level fluctuations varying between 3 to 4.8m (refer Table 2.4, section 2.4.1.2 and Annex 2.1, 2.2 and 2.3). a. Dewatered Section Impact Figure 6.1 shows the comparative account of the mean annual hydrograph of the Kabeli River in the dewatered section for the existing conditions and during operation period if all the water is diverted to design capacity to maximize power production. The graph shows that during the dry months, most of the water will be diverted except for the allocated minimum ecological release. 
To give more precise information on the effect of water withdrawal to the Kabeli A powerhouse, we should consider measured flows, which are now available for Kabeli for the past three years. KEL installed a gauging station in Kabeli in 2010. Figures 6.2 and 6.3 show all flows measured in 2011 and 2012 respectively. Also, refer to Figure 4.5 (Chapter 4). More data will be available from the monitoring of flow in the coming years that can be used to further develop mitigation measures for the flow management in the dewatered section. Figures 6.2:Observed real time flow data for 2011 
Source: KEL, 2013 Figure 6.3: Observed real time flow data for 2012 
Source: KEL, 2013 Figure 6.4: Actual flow data for dry months (November 2011-May 2012) 
Source: KEL, 2013 The project is planned as a peaking Run-of-River (PRoR) type project with a reservoir of 2 and 4 hours of morning and evening peaking capacity. Figure 6.5 demonstrates how the peaking operation will be run during a typical day. The water from Kabeli will be diverted to Tamor River for power generation. Therefore, the peaking operations will not affect the dewatered section in the Kabeli River. At the powerhouse site, the operations of the power station will affect the Tamor river through the water added by the tailrace channel. The resulting hydrograph is shown in Figure 6.5. Figure 6.5: Tamor River flow data below the Kabeli-A a tailrace with and without operation. 
Source: KEL, 2013 Blue lines shows the natural flow in Tamor and the red line shows the natural flow and the additional peaking flow from the power house. If all water at dam site will be diverted, there will be only seepage, groundwater and discharge from the three small streams in Kabli downstream the dam (Refer Table 4.12).The available seepage and groundwater in the river will not be sufficient to sustain the existing aquatic life. Three small streams (Sarki Khola at 1.2 km, Andheri Khola at 1.6 km, and Khahare Khola at 3 km downstream from the dam) join Kabeli with total flow contribution of 0.18 m3/s during the dry month of April. Without any mitigation measures, the dewatered section of Kabeli River to the confluence of Tamor River would likely to be devoid of majority of the existing aquatic life for nearly 7 months in a year. However, after the confluence (5.6 km downstream from the dam), the flow in the Tamor Riveris high enough to maintain the existing aquatic life and community water requirements. The minimum flow in the Tamor River before confluence with Kabeli is estimated to be about 23 m3/s in the month of March. Therefore, the expected long term aquatic habitat conversion will occur at the Kabeli river diversion (dewatered section) and at the Tamor downstream from the powerhouse’s tailrace due to daily discharge fluctuation during peak generation.
According to Dyson et.al (2003), the downstream release flow regime commonly referred to as the Ecological Flow, is “the water regime provided within a river, wetland or coastal zone to maintain ecosystems and their benefits where there are competing water uses and where flows are regulated”. How this flow is determined is a question of debate among ecologists, developers and other water user stakeholders. However, all stakeholders agree that the choice of environmental flow requirements should be based on informed scientific decision and broad societal acceptance. For Kabeli-A, the objective of releasing the downstream environmental flow is to keep the ecological river corridor open and to secure survival of substantial amounts of fry and fingerlings of target species in the dewatered zone (refer Table 6.10 for selected target species). For a social point of view, the objective is to ensure continuation of the local people’s traditional activities connected to the river. The question of environmental flow management particularly related to hydropower development (run of the River or Reservoir projects) is at the central arena of discussion in Nepal. The downstream flow management has become a critical issue particularly in rivers where survey license for hydropower development are issued in a cascade fashion. The existing legal instruments (Aquatic Animal Protection Act, 1998 and Hydropower Development Policy, 2001) have set ad-hoc environmental flow requirements downstream the water diversion points without any scientific basis. Again, the legally purposed environmental flow differs widely. Aquatic Animal Protection Act stipulates a provision of minimum 5% of yearly minimum flow, whereas the Hydropower Development Policy recommends 10% of the minimum monthly average discharge of the river/stream or the minimum required quantum as identified in the EIA study report. By the amount of water volume, the provisions of the Hydropower Development Policy is better than the Aquatic Animal Protection Act, however, still lacks a scientific basis in setting the environmental flow regime requirements to sustain the rivers’ natural social and ecological functions. The discussion on the downstream environmental flow requirements in the sections below the dam is limited to the KAHEP project. The environmental flow requirements objectives for KAHEP are based on the following project features and baseline.
Project features and baseline reflect that the environmental flow requirement for the project is mainly for the dry season (November through May) when the project design flow requirement is higher than the Kabeli River natural discharge. In this period, if water is not released from the dam, there will not be enough water in the dewatered section of the Kabeli for community non-consumptive uses (mainly cremation, religious bath etc.),nor for the maintenance of the ecological corridor in the Kabeli and to secure survival of fry and fingerlings of the target species (refer Table 6.10 ) in the dewatered section. During wet season, it seems likely that the flow regime will be enough for migration and spawning to take place as if under natural flow conditions. With the above objectives, the environmental flow requirement is analyzed and evaluated in the section below:
The diversion of the flow for power generation will affect religious and cultural activities in the riverbank and cremation sites “Ghats” where dead bodies are burnt. Flowing water with certain depth (usually waist depth) is required to perform cultural and religious activities like bathing through dipping in the river and for throwing the burnt ashes of the dead bodies. The waist deep water may be created in pool or channel. The water requirement for the above purpose is broadly defined as non-consumptive use. This means, there will be no loss of water even after use and is available for further downstream users. In this context, cleanliness requirement, i.e. the minimum discharge of water to keep the river wet stretch clean is the water quality requirement for the above uses. The location of religious and cremation sites is shown in Figure 6.6. Figure 6.6: Location of Religious and Cremation Sites downstream the Dam 
Flow, water quality, temperature, energy spiral, gravel bed composition and sediment load are key factors in formation of the river ecosystems. The matter of complexity concerning number of species is a function of their ability to migrate into certain areas, and a function of the species requirements for ecosystem services and completion of their life cycles. The species flexibility and adaption capacity are key factors on the gene pool level of a population and on its overall resilience to disturbances. Tamor and Kabeli seem to have high species diversity. The productivity in the river ecosystems will typically come from input of organic matter. This organic matter might be produced within the river by algae, moss and macrophytes or it might be riparian organic matter originating from the surroundings. The latter is normally the main source of primary productivity in river ecosystems. In the affected sections of Kabeli and Tamor Rivers, the environmental conditions significantly differ. Understanding the differences is crucial to determine sources of primary and secondary productivity, and define the overall ecological integrity of the affected segments:
An effect of flow in river systems is related to the allocation of energy components to the food chain along the river. Organic matter is the main source of energy and “building blocks” to the formation of biomass in the river ecosystems. Since all ochtonous matter is the dominating energy source to the food chain, river flow regime is crucial to the transformation of organic matter to biomass. High velocity waters give low local effectiveness in transformation from organic matter to biomass due to shorter retention periods. In low velocity sections of the river, as in the dewatered section, it is reasonable to assume that the organic matter from the surroundings will have a higher transformation rate to biomass during low flow season. This difference in water velocity is one of the main reasons for explaining why small rivers tend to be more productive than bigger rivers. In Himalayan Rivers, the hydrological fluctuations over the year cycle are significant. Monsoon with high flow and high sediment load is normal and the fauna and flora has adapted their lifecycle to these conditions. The temperature is crucial to metabolism and growth in aquatic environment and the temperature gradients in the rivers are the basis for development of key cues and features of these species life cycles and their adaption to cold and warm waters. The KAHEP is a RoR project with a limited daily peaking reservoir in the dry season (November through May). Even during the low flow regulated conditions without precipitation in the dry season, there will normally be groundwater inlet to the river and flow from three small tributaries. There might also be limited seepage from the reservoir. At this early, stage it is hard to assess if these would represent a significant contribution to environmental flow in the dewatered section. It must be noted that even without any environmental flow release from the Kabeli-A dam, the flow after Kabeli Bazzar (about 3 km downstream of the dam) during the lowest flow conditions has been estimated to be about 0.48 m3/s. The tributaries below dam (refer Table 4.12, Table 6.11 and Figure 4.6) are expected to contribute to nearly 0.18 m3/s of discharge, and an additional 0.3 m3/s discharge is expected from groundwater contribution (personal experience of the consultant from Lower Marsyangdi dewatered section - Refer EIA study MMHEP, 2001).
Calculation of Environmental flow can be done through a number of methods. This EIA has approached this calculation in an evolving fashion. Initially, based on Nepali current practice and existing legal instruments (Aquatic Animal Protection Act, 1998 and Hydropower Development Policy, 2001), it started with a modified Tenant Method approach. However, this analysis evolved and was refined based on consultation with global experts and experience and data from other projects in Nepal. Keeping in view the expected flow variations in the KAHEP, reviews of the environmental flow methodologies applied in Nepal and elsewhere were examined for the Environmental flow (EF) estimations. The methodologies are differentiated into hydrological, hydraulic rating, habitat simulation and holistic methodologies, with a further two categories representing combination-type and other approaches (Tharme 2003). All the methodologies have targeted objectives of environmental flow and cover broader to specific ecological and/or social issues. The choice of methodology for the analysis of environmental flow is a choice of the set of objectives for a development project. Without setting objectives of the environmental flow, random application of the available EF methodologies could lead to confusion or ineffective solutions. In this context, what is important is to understand the local hydrological conditions (flow variations – daily, monthly, and yearly) in relation to human water uses/ needs and the thriving ecology of the targeted fauna and flora while applying the environmental flow methodologies developed in distant parts of the world with different set of hydrology and socio-ecological relationship and needs. A few projects such as Kali Gandaki “A” and Middle Marsyangdi in Nepal have applied the hydrological methods established by Tenant also called Tenant Method (1975) with some modifications to estimate the environmental flow. These hydrological methodologies rely primarily on the use of hydrological data, usually in the form of naturalized, historical monthly or daily flow records, for making environmental flow recommendations (Tharme 2003). These methods are often referred to as fixed-percentage or look-up table methodologies, where a set proportion of flow, often termed the minimum flow represents the EF intended to maintain the freshwater fishery, other highlighted ecological or social features, or river integrity at some acceptable level, usually on an annual, seasonal or monthly basis. The modification of the Tenant Method (1975) was envisaged because direct application of the hydrological method as adopted by Tenant in North America, using only the average six monthly flows (October to March and April to September) and applied only to salmonids of the US, could not address the hydrological fluctuations of the Nepalese rivers. Table 6.5 and Table 6.6 present the differences of the Tenant Method (1975) and Modified Tenant Method (EIA Kali Gandaki “A” and Middle Marsyangdi) when applied to the KAHEP. Table 6.5: In-stream flow for fish, wildlife, and recreation (Tennant 1975)
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